Heat advisories issued for most of the area MYRTLE BEACH, S.C. (WBTW) — Humidity is increasing today, along with slightly higher temperatures, leading to a Heat Advisory for more than half of the area. Marion, Dillon, Marlboro, Scotland, Robeson, and most of Horry County — excluding the Grand Strand beaches — are under a Heat Advisory until 8 p.m. Heat index values will climb above 105, and heat alerts will likely become even more widespread across the area tomorrow.